=== SEC Form 4 — Statement of Changes in Beneficial Ownership ===
Document Type: 4
Period of Report: 2026-05-06
10b5-1 Pre-arranged Plan: No
--- Issuer ---
Name: MONOLITHIC POWER SYSTEMS INC (MPWR)
CIK: 0001280452
--- Reporting Owner ---
Name: Xiao Deming
CIK: 0001308647
Role: Officer (EVP, Global Operations)
--- Non-Derivative Transactions ---
[Transaction #1]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -3,329 | Price: $1,648.38
Total Value: $5,487,457.02
Shares Owned After: 232,630 | Ownership: D (Direct)
Footnotes:
[F2] The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,645.48 to $1,650.43. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
[F1] Ending balance includes 27 shares acquired on February 17, 2026 through the Company's qualified ESPP program.
[Transaction #2]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -14,167 | Price: $1,652.80
Total Value: $23,415,217.60
Shares Owned After: 218,463 | Ownership: D (Direct)
Footnotes:
[F3] The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,650.75 to $1,655.75. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
[Transaction #3]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -11,597 | Price: $1,657.93
Total Value: $19,227,014.21
Shares Owned After: 206,866 | Ownership: D (Direct)
Footnotes:
[F4] The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,655.80 to $1,660.72. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
[Transaction #4]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -907 | Price: $1,661.38
Total Value: $1,506,871.66
Shares Owned After: 205,959 | Ownership: D (Direct)
Footnotes:
[F5] The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,660.99 to $1,662 The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
--- Holdings ---
[Holding #1]
Security: Common Stock
Ownership: I (Indirect)
[Holding #2]
Security: Common Stock
Ownership: I (Indirect)
--- Footnotes (Complete Index) ---
F1: Ending balance includes 27 shares acquired on February 17, 2026 through the Company's qualified ESPP program.
F2: The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,645.48 to $1,650.43. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
F3: The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,650.75 to $1,655.75. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
F4: The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,655.80 to $1,660.72. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
F5: The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $1,660.99 to $1,662 The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
--- Signature ---
/s/ /s/ Saria Tseng, attorney-in-fact for Mr. Deming Xiao (2026-05-08)
